Magnetic random access memory (MRAM or “MagRAM”) is a solid-state device using magnetic thin film elements as a storage mechanism. The storage mechanism is dependent upon the relative orientation of the magnetization of two electrodes, and on the ability to detect this orientation by electrical means. MRAM arrays typically include an array of magnetic memory cells positioned at the intersections of wordlines and bitlines. Generally, each cell includes a magnetically changeable or “free” region, and a nearby magnetic reference region, arranged into a magnetic tunnel junction (“MTJ”) device.
The principle underlying storage of data in these memory cells is the ability to change the relative orientation of the magnetization of the free and reference regions by changing the direction of magnetization along the easy axis (“EA”) of the free region, and the ability to read this relative orientation difference thereafter. An MRAM cell is written by reversing the free region magnetization using applied bi-directional electrical and resultant magnetic stimuli via its received bitline and wordline. The MRAM cell is read by measuring the resultant tunneling resistance between the bitline and wordline, which assumes one of two values depending on the relative orientation of the magnetization of the free region with respect to the reference region. If the free region is modeled as a simple elemental magnet having a direction of magnetization which is free to rotate, but with a strong preference for aligning in either direction along its easy axis (+EA or −EA), and if the reference region is a similar elemental magnet but having a direction of magnetization fixed in the +EA direction, two states (and the two possible tunneling resistance values) are defined for the cell: aligned (+EA/+EA) and an-aligned (−EM +EA).
In operation, the MRAM device can be read by measuring the tunneling resistance to infer the magnetization state of the storage layer with respect to the fixed layer. The MRAM can be written by reversing the free layer magnetization using external magnetic fields. If the free layer is imagined as a simple elemental magnet which is free to rotate but with a strong energetic preference for aligning parallel to the X axis, and if the pinned layer is a similar elemental magnet but frozen in the +X direction, then there is at least two states possible for the device (e.g., aligned and anti-aligned in +X or −X directions).
In order to produce magnetic switching devices efficiently and with consistent results, there is a need for a method of fabricating and patterning the various layers of a magnetic switching device such that consistent results may be obtained.